1. Field of the Invention
The present invention relates to an optical waveguide for a touch panel, a touch panel using the optical waveguide, and a manufacturing method of the optical waveguide for a touch panel.
2. Description of the Related Art
Touch panels are input devices for operating an apparatus by directly touching a display screen of a liquid crystal display device or the like with a finger, a purpose-built stylus or the like, and include a display which displays operation details and the like, and a detection means which detects the position (coordinates) of a portion of the display screen of the display touched with the finger or the like. Information about the touch position detected by the detection means is sent in the form of a signal to the apparatus, which in turn performs an operation and the like displayed on the touch position. Examples of the apparatus employing such a touch panel include ATMs in banking facilities, ticket vending machines in stations, portable game machines, and the like.
A detection means employing an optical waveguide is proposed as the detection means for detecting the finger touch position and the like on the above-mentioned touch panel (see, for example, US 2006/0002655A1). Specifically, the touch panel includes a strip-shaped optical waveguide 70 wound on peripheral side surfaces of a rectangular display 11, and a rectangular frame-shaped lens 71 provided on an upper edge portion of a display screen of the above-mentioned display 11, as shown in FIG. 7. A multiplicity of cores which pass light beams therethrough are formed in the above-mentioned optical waveguide 70. With the optical waveguide 70 wound as described above, first end surfaces (light emitting surfaces and light receiving surfaces) of the respective cores are formed so as to be oriented toward the above-mentioned frame-shaped lens 71. A multiplicity of light beams emitted from a portion of the optical waveguide 70 provided on one side portion of the peripheral side surfaces of the display 11 are caused to change the direction of their paths so as to travel in parallel with the display screen of the display 11 by a first portion of the above-mentioned frame-shaped lens 71, and thereafter are caused to change the direction of their paths so as to enter a portion of the optical waveguide 70 provided on the other side portion by a second portion of the frame-shaped lens 71 opposed to the first portion thereof. In this manner, the above-mentioned optical waveguide 70 and the frame-shaped lens 71 cause the light beams to travel in a lattice form on the display screen of the display 11. When a portion of the display screen of the display 11 is touched with a finger in this state, the finger blocks some of the light beams. Therefore, the light-receiving portion of the optical waveguide 70 senses a light blocked portion, whereby the position of the portion touched with the finger is detected.
For a touch panel using the above-mentioned optical waveguide 70, it is necessary that the light beams emitted from the light-emitting portion of the optical waveguide 70 into the air be incident on the cores of the light-receiving portion of the optical waveguide 70. In this case, when the emitted light beams spread too wide, there is a low probability that the light beams enter the cores of the light-receiving portion, which results in low optical transmission efficiency. Narrowing down the emitted light beams too much, on the other hand, reduces the size of a light-receiving region to make it difficult for the cores of the light-receiving portion to receive the light beams (or to make it impossible for the cores of the light-receiving portion to receive the light beams if the cores of the light-receiving portion are deviated from their proper position even slightly).
In the touch panel using the above-mentioned optical waveguide 70, the light beams do not appropriately pass through the frame-shaped lens 71 so that the optical transmission efficiency is not sufficiently enhanced unless precise alignment is performed between the optical waveguide 70 and the frame-shaped lens 71. Additionally, the precise alignment requires accuracy and is hence difficult. It is labor- and time-consuming to achieve the precise alignment.